Web/API/MouseEvent/which

Non-standard This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The MouseEvent.which read-only property indicates which button was pressed on the mouse to trigger the event. The standard alternatives to this property are MouseEvent.button and MouseEvent.buttons.

Syntax

var buttonPressed = instanceOfMouseEvent.which

Return value

A number representing a given button:

0: No button
1: Left button
2: Middle button (if present)
3: Right button

For a mouse configured for left-handed use, the button actions are reversed. In this case, the values are read from right to left.

Specification

This is not part of any specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`which` Non-standard'	Chrome Full support 1	Edge Full support 12	Firefox Full support 1 Notes' Full support 1 Notes' Notes' On `mousemove` events, the `which` property is incorrectly always set to `1`.	IE Full support 9	Opera Full support 10.6	Safari Full support 3.1	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4 Notes' Full support 4 Notes' Notes' On `mousemove` events, the `which` property is incorrectly always set to `1`.	Opera Android Full support 11	Safari iOS Full support Yes	Samsung Internet Android Full support Yes

Legend

Full support: Full support
Non-standard. Expect poor cross-browser support.': Non-standard. Expect poor cross-browser support.
See implementation notes.': See implementation notes.